Showing papers by "J. Pluta published in 2018"

Global polarization of Λ hyperons in Au + Au collisions at sNN =200 GeV

Abstract: Global polarization of $\Lambda$ hyperons has been measured to be of the order of a few tenths of a percent in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV, with no significant difference between $\Lambda$ and $\bar{\Lambda}$. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at $\sqrt{s_{_{NN}}}$ = 7.7 -- 62.4 GeV and indicate noticeable vorticity of the medium created in non-central heavy-ion collisions at the highest RHIC collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from the AMPT (A Multi-Phase Transport) model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity $\eta^H$ within $|\eta^H|<1$. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the $2\sigma$ level, suggesting a possible contribution to the polarization from the axial current induced by the initial magnetic field.

Energy dependence and fluctuations of anisotropic flow in Pb-Pb collisions at √sNN = 5.02 and 2.76 TeV

Abstract: Measurements of anisotropic flow coefficients with two- and multi-particle cumulants for inclusive charged particles in Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ and 2.76 TeV are reported in the pseudorapidity range |η| < 0.8 and transverse momentum 0.2 < p$_{T}$ < 50 GeV/c. The full data sample collected by the ALICE detector in 2015 (2010), corresponding to an integrated luminosity of 12.7 (2.0) μb$^{−1}$ in the centrality range 0-80%, is analysed. Flow coefficients up to the sixth flow harmonic (v$_{6}$) are reported and a detailed comparison among results at the two energies is carried out. The p$_{T}$ dependence of anisotropic flow coefficients and its evolution with respect to centrality and harmonic number n are investigated. An approximate power-law scaling of the form v$_{n}$(p$_{T}$) ∼ p$_{T}^{n}^{/3}$ is observed for all flow harmonics at low p$_{T}$ (0.2 < p$_{T}$ < 3 GeV/c). At the same time, the ratios v$_{n}$/v$_{m}^{n}^{/ }^{m}$ are observed to be essentially independent of p$_{T}$ for most centralities up to about p$_{T}$ = 10 GeV/c. Analysing the differences among higher-order cumulants of elliptic flow (v$_{2}$), which have different sensitivities to flow fluctuations, a measurement of the standardised skewness of the event-by-event v$_{2}$ distribution P(v$_{2}$) is reported and constraints on its higher moments are provided. The Elliptic Power distribution is used to parametrise P(v$_{2}$), extracting its parameters from fits to cumulants. The measurements are compared to different model predictions in order to discriminate among initial-state models and to constrain the temperature dependence of the shear viscosity to entropy-density ratio.

D-meson azimuthal anisotropy in midcentral Pb-Pb collisions at √sNN=5.02 TeV

Abstract: A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung fur Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep), and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Brazil; Ministry of Science and Technology of China (MSTC), National Natural Science Foundation of China (NSFC) and Ministry of Education of China (MOEC), China; Ministry of Science, Education and Sport and Croatian Science Foundation, Croatia; Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research–Natural Sciences, the Carlsberg Foundation, and Danish National Research Foundation (DNRF), Denmark; Helsinki Institute of Physics (HIP), Finland; Commissariat a l’Energie Atomique (CEA) and Institut National de Physique Nucleaire et de Physique des Particules (IN2P3) and Centre National de la Recherche Scientifique (CNRS), France; Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie (BMBF) and GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Germany; General Secretariat for Research and Technology, Ministry of Education, Research and Religions, Greece; National Research, Development and Innovation Office, Hungary; Department of Atomic Energy Government of India (DAE) and Council of Scientific and Industrial Research (CSIR), New Delhi, India; Indonesian Institute of Science, Indonesia; Centro Fermi—Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi and Istituto Nazionale di Fisica Nucleare (INFN), Italy; Institute for Innovative Science and Technology, Nagasaki Institute of Applied Science (IIST), Japan Society for the Promotion of Science (JSPS) KAKENHI, and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnologia, through Fondo de Cooperacion Internacional en Ciencia y Tecnologia (FONCICYT) and Direccion General de Asuntos del Personal Academico (DGAPA), Mexico; Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Netherlands; The Research Council of Norway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Universidad Catolica del Peru, Peru; Ministry of Science and Higher Education and National Science Centre, Poland; Korea Institute of Science and Technology Information and National Research Foundation of Korea (NRF), Republic of Korea; Ministry of Education and Scientific Research, Institute of Atomic Physics, and Romanian National Agency for Science, Technology and Innovation, Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education and Science of the Russian Federation, and National Research Centre Kurchatov Institute, Russia; Ministry of Education, Science, Research and Sport of the Slovak Republic, Slovakia; National Research Foundation of South Africa, South Africa; Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Cubaenergia, Cuba, Ministerio de Ciencia e Innovacion and Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Spain; Swedish Research Council (VR) and Knut and Alice Wallenberg Foundation (KAW), Sweden; European Organization for Nuclear Research, Switzerland; National Science and Technology Development Agency (NSDTA), Suranaree University of Technology (SUT), and Office of the Higher Education Commission under NRU project of Thailand, Thailand; Turkish Atomic Energy Agency (TAEK), Turkey; National Academy of Sciences of Ukraine, Ukraine; Science and Technology Facilities Council (STFC), United Kingdom; National Science Foundation of the United States of America (NSF) and United States Department of Energy, Office of Nuclear Physics (DOE NP), United States of America.

Beam-Energy Dependence of Directed Flow of Λ, Λ[over ¯], K^{±}, K_{s}^{0}, and ϕ in Au+Au Collisions.

Abstract: Rapidity-odd directed-flow measurements at midrapidity are presented for Λ, Λ[over ¯], K^{±}, K_{s}^{0}, and ϕ at sqrt[s_{NN}]=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV in Au+Au collisions recorded by the Solenoidal Tracker detector at the Relativistic Heavy Ion Collider. These measurements greatly expand the scope of data available to constrain models with differing prescriptions for the equation of state of quantum chromodynamics. Results show good sensitivity for testing a picture where flow is assumed to be imposed before hadron formation and the observed particles are assumed to form via coalescence of constituent quarks. The pattern of departure from a coalescence-inspired sum rule can be a valuable new tool for probing the collision dynamics.

Low- pT e+e- Pair Production in Au +Au Collisions at sNN =200 GeV and U + U Collisions at sNN =193 GeV at STAR

Abstract: Author(s): Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Atetalla, F; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderon de la Barca Sanchez, M; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, F-H; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, JH; Chen, X; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Galatyuk, T | Abstract: We report first measurements of e^{+}e^{-} pair production in the mass region 0.4

π0 and η meson production in proton-proton collisions at √s = 8 TeV

Abstract: An invariant differential cross section measurement of inclusive $$\pi ^{0}$$ and $$\eta $$ meson production at mid-rapidity in pp collisions at $$\sqrt{s}=8$$ TeV was carried out by the ALICE experiment at the LHC. The spectra of $$\pi ^{0}$$ and $$\eta $$ mesons were measured in transverse momentum ranges of $$0.33.5$$ $$\text{ GeV/c }$$ . However, a deviation from this empirical scaling rule is observed for transverse momenta below $$p_{ \text{ T }} <3.5$$ $$\text{ GeV/c }$$ in the $$\eta /\pi ^0$$ ratio with a significance of $$6.2\sigma $$ .

Measurement of prompt D0, D+, D∗+, and D+s production in p–Pb collisions at √sNN = 5.02 TeV

Abstract: We report measurements of the production of prompt D$^{0}$, D$^{+}$, D$^{*+}$ and D$_{s}^{+}$ mesons in Pb–Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV, in the centrality classes 0–10%, 30–50% and 60–80%. The D-meson production yields are measured at mid-rapidity (|y| 8 GeV/c, while it is larger at lower p$_{T}$. The nuclear modification factors for strange and non-strange D mesons are also compared to theoretical models with different implementations of in-medium energy loss.

Measurement of the H Λ3 lifetime in Au+Au collisions at the BNL Relativistic Heavy Ion Collider

Abstract: Author(s): Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Alford, J; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bhattarai, P; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Bouchet, J; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderon De La Barca Sanchez, M; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, X; Chen, X; Chen, JH; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deng, J; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Draper, JE; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Feng, Z; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fujita, J | Abstract: An improved measurement of the HΛ3 lifetime is presented. In this paper, the mesonic decay modes HΛ3→He3 + π- and HΛ3→d+p+π- are used to reconstruct the HΛ3 from Au+Au collision data collected by the STAR collaboration at Relativistic Heavy Ion Collider (RHIC). A minimum χ2 estimation is used to determine the lifetime of τ=142-21+24(stat.)±29(syst.) ps. This lifetime is about 50% shorter than the lifetime τ=263±2 ps of a free Λ, indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R.(He3+π-)/(B.R.(He3+π-)+B.R.(d+p+π-))=0.32±0.05(stat.)±0.08(syst.). Our ratio result favors the assignment J(HΛ3)=12 over J(HΛ3)=32. These measurements will help to constrain models of hyperon-baryon interactions.

Harmonic decomposition of three-particle azimuthal correlations at energies available at the BNL Relativistic Heavy Ion Collider

Abstract: Author(s): Adamczyk, L; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bhattarai, P; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Bouchet, J; Brandenburg, JD; Brandin, AV; Brown, D; Bunzarov, I; Butterworth, J; Caines, H; Sanchez, M Calderon de la Barca; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, X; Chen, JH; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; De Silva, LC; Debbe, RR; Dedovich, TG; Deng, J; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Draper, JE; Dunkelberger, LE; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Feng, Z; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Garand, D; Geurts, F | Abstract: We present measurements of three-particle correlations for various harmonics in Au+Au collisions at energies ranging from $\sqrt{s_{{\rm NN}}}=7.7$ to 200 GeV using the STAR detector. The quantity $\langle\cos(m\phi_1+n\phi_2-(m+n)\phi_3)\rangle$ is evaluated as a function of $\sqrt{s_{{\rm NN}}}$, collision centrality, transverse momentum, $p_T$, pseudo-rapidity difference, $\Delta\eta$, and harmonics ($m$ and $n$). These data provide detailed information on global event properties like the three-dimensional structure of the initial overlap region, the expansion dynamics of the matter produced in the collisions, and the transport properties of the medium. A strong dependence on $\Delta\eta$ is observed for most harmonic combinations consistent with breaking of longitudinal boost invariance. Data reveal changes with energy in the two-particle correlation functions relative to the second-harmonic event-plane and provide ways to constrain models of heavy-ion collisions over a wide range of collision energies.

Beam Energy Dependence of Jet-Quenching Effects in Au+Au Collisions at sqrt[s_{NN}]=7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV.

Abstract: We report measurements of the nuclear modification factor R_{CP} for charged hadrons as well as identified π^{+(-)}, K^{+(-)}, and p(p[over ¯]) for Au+Au collision energies of sqrt[s_{NN}]=7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe a clear high-p_{T} net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra but is also very similar for the kaon spectra. While the magnitude of the proton R_{CP} at high p_{T} does depend on the collision energy, neither the proton nor the antiproton R_{CP} at high p_{T} exhibit net suppression at any energy. A study of how the binary collision-scaled high-p_{T} yield evolves with centrality reveals a nonmonotonic shape that is consistent with the idea that jet quenching is increasing faster than the combined phenomena that lead to enhancement.

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at s = 500 GeV

Abstract: Author(s): AdamczyK, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bhattarai, P; BielciK, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Bouchet, J; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderon De La Barca Sanchez, M; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, X; Chen, X; Chen, JH; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deng, J; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Draper, JE; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Feng, Z; Filip, P; Finch, E; FisyaK, Y; Flores, CE; Fujita, J; FuleK, L | Abstract: We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet+π± production at midrapidity from transversely polarized proton-proton collisions at s=500 GeV. The data were collected in 2011 with the STAR detector sampled from 23 pb-1 integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta 6

Azimuthal anisotropy in Cu+Au collisions at s NN =200 GeV

Abstract: The azimuthal anisotropic flow of identified and unidentified charged particles has been systematically studied in Cu+Au collisions at sNN=200 GeV for harmonics n=1–4 in the pseudorapidity range |η|<1. The directed flow in Cu+Au collisions is compared with the rapidity-odd and, for the first time, the rapidity-even components of charged particle directed flow in Au+Au collisions at sNN=200 GeV. The slope of the directed flow pseudorapidity dependence in Cu+Au collisions is found to be similar to that in Au+Au collisions, with the intercept shifted toward positive pseudorapidity values, i.e., the Cu-going direction. The mean transverse momentum projected onto the spectator plane 〈px〉 in Cu+Au collision also exhibits approximately linear dependence on pseudorapidity with the intercept at about η≈−0.4 (shifted from zero in the Au-going direction), closer to the rapidity of the Cu+Au system center of mass. The observed dependencies find a natural explanation in a picture of the directed flow originating partly due the “tilted source” and partly due to the asymmetry in the initial density distribution. A charge dependence of 〈px〉 was also observed in Cu+Au collisions, consistent with an effect of the initial electric field created by charge difference of the spectator protons in two colliding nuclei. The rapidity-even component of directed flow in Au+Au collisions is close to that in Pb+Pb collisions at sNN=2.76 TeV, indicating a similar magnitude of dipolelike fluctuations in the initial-state density distribution. Higher harmonic flow in Cu+Au collisions exhibits similar trends to those observed in Au+Au and Pb+Pb collisions and is qualitatively reproduced by a viscous hydrodynamic model and a multiphase transport model. For all harmonics with n≥2 we observe an approximate scaling of vn with the number of constituent quarks; this scaling works as well in Cu+Au collisions as it does in Au+Au collisions.

Erratum: Observation of D^{0} Meson Nuclear Modifications in Au+Au Collisions at sqrt[s_{NN}]=200 GeV [Phys. Rev. Lett. 113, 142301 (2014)].

Abstract: This corrects the article DOI: 10.1103/PhysRevLett.113.142301.

Neutral pion and η meson production at midrapidity in Pb-Pb collisions at √sNN=2.76 TeV

Abstract: Neutral pion and η meson production in the transverse momentum range 1

Longitudinal double-spin asymmetries for dijet production at intermediate pseudorapidity in polarized pp collisions at s =200 GeV

Abstract: Author(s): Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Atetalla, F; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderon De La Barca Sanchez, M; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, FH; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, JH; Chen, X; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Galatyuk, T | Abstract: We present the first measurements of the longitudinal double-spin asymmetry ALL for dijets with at least one jet reconstructed within the pseudorapidity range 0.8lηl1.8. The dijets were measured in polarized pp collisions at a center-of-mass energy s=200 GeV. Values for ALL are determined for several distinct event topologies, defined by the jet pseudorapidities, and span a range of parton momentum fraction x down to x∼0.01. The measured asymmetries are found to be consistent with the predictions of global analyses that incorporate the results of previous RHIC measurements. They will provide new constraints on Δg(x) in this poorly constrained region when included in future global analyses.

Longitudinal double-spin asymmetries for p0s in the forward direction for 510 GeV polarized pp collisions

Abstract: Author(s): Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Ajitanand, NN; Alekseev, I; Anderson, DM; Aoyama, R; Aparin, A; Arkhipkin, D; Aschenauer, EC; Ashraf, MU; Atetalla, F; Attri, A; Averichev, GS; Bai, X; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bhati, AK; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Brown, D; Bryslawskyj, J; Bunzarov, I; Butterworth, J; Caines, H; Calderon De La Barca Sanchez, M; Campbell, JM; Cebra, D; Chakaberia, I; Chaloupka, P; Chang, FH; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chattopadhyay, S; Chen, JH; Chen, X; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, HJ; Das, S; Dedovich, TG; Deppner, IM; Derevschikov, AA; Didenko, L; Dilks, C; Dong, X; Drachenberg, JL; Dunlop, JC; Efimov, LG; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Federicova, P; Fedorisin, J; Filip, P; Finch, E; Fisyak, Y; Flores, CE; Fulek, L; Gagliardi, CA; Galatyuk, T | Abstract: The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, ALL, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass energy of 510 GeV. Results are given for transverse momenta in the range 2

Correlation Measurements Between Flow Harmonics in Au+Au Collisions at RHIC

Abstract: Flow harmonics ($v_n$) in the Fourier expansion of the azimuthal distribution of particles are widely used to quantify the anisotropy in particle emission in high-energy heavy-ion collisions. The symmetric cumulants, $SC(m,n)$, are used to measure the correlations between different orders of flow harmonics. These correlations are used to constrain the initial conditions and the transport properties of the medium in theoretical models. In this Letter, we present the first measurements of the four-particle symmetric cumulants in Au+Au collisions at $\sqrt{s_{NN}}$ = 39 and 200 GeV from data collected by the STAR experiment at RHIC. We observe that $v_{2}$ and $v_{3}$ are anti-correlated in all centrality intervals with similar correlation strengths from 39 GeV Au+Au to 2.76 TeV Pb+Pb (measured by the ALICE experiment). The $v_{2}$-$v_{4}$ correlation seems to be stronger at 39 GeV than at higher collision energies. The initial-stage anti-correlations between second and third order eccentricities are sufficient to describe the measured correlations between $v_{2}$ and $v_{3}$. The best description of $v_{2}$-$v_{4}$ correlations at $\sqrt{s_{NN}}$ = 200 GeV is obtained with inclusion of the system's nonlinear response to initial eccentricities accompanied by the viscous effect with $\eta/s$ $>$ 0.08. Theoretical calculations using different initial conditions, equations of state and viscous coefficients need to be further explored to extract $\eta/s$ of the medium created at RHIC.

Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{NN}}$= 27, 39, and 62.4 GeV from the STAR Experiment.

Abstract: We report systematic measurements of dielectron ($e^{\pm}e^{\pm}$) invariant-mass $M_{ee}$ spectra at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (0.40$ < M_{ee} < 0.75$ MeV/$c^2$) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the $\rho$-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au+Au collisions at mid-rapidity ($\left|y_{ee}\right|$ $<$ 1) in the 0$-$80% centrality bin for each collision energy. The integrated excess yields for $0.4 < M_{ee} < 0.75\ \textrm{GeV}/c^{2}$, normalized by the charged particle multiplicity at mid-rapidity, are compared with previously published measurements for Au+Au at $\sqrt{s_{NN}}$ = 19.6 and 200 GeV. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.

$J/\psi$ production cross section and its dependence on charged-particle multiplicity in $p+p$ collisions at $\sqrt{s}$ = 200 GeV

Abstract: We present a measurement of inclusive $J/\psi$ production at mid-rapidity ($|y|<1$) in $p+p$ collisions at a center-of-mass energy of $\sqrt{s}$ = 200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The differential production cross section for $J/\psi$ as a function of transverse momentum ($p_T$) for $0